1. Field of the Invention
THIS INVENTION relates to load-bearing rings for hydraulic fasteners and hydraulic tensioning devices, and other tensioning devices.
The hydraulic fasteners and hydraulic tensioning devices are operable to fasten one or more parts together. The hydraulic fasteners may comprise an hydraulic nut or washer; while the hydraulic tensioning devices may comprise tensioning rings particularly suitable for, but not limited to, closing flange joints on pipe lines, valves and the like.
2. Prior Art
The use of fasteners employing hydraulic operating components to apply bolt tension is well-established. Examples can be found in U.S. Pat. No. 5,730,569 (Bucknell) (=International Application PCT/AU93/00477=International Publication WO 94/07042). Further examples can be found in the “References Cited” on U.S. Pat. No. 5,730,569.
Such fasteners are intended to be installed in a manner allowing the periodic removal of the service or maintenance on the equipment to which they are fixed. Such fasteners are seldom used in situations where they may be permanently applied.
Tension release systems have preferred use in a closed system incorporating a tensile member applying a clamping force to fasten the assembly, for example, simple bolt and nut systems of such applications as the bolting of flanges or other mechanical components.
Tensile members such as bolts and shafts and such arrangements apply clamping forces to subject components as a result of their being elongated by known bolt-tightening methods and consequently seeking to return to their free length. It is a known practice that in situations where the capacity to de-tension the member, by the reversal of the method of application, may be diminished or impractical to place a sacrificial component, such as a washer, into the assembly. In such circumstances, the washer may be removed by force, or by cutting it with an oxy-acetylene torch in order to allow the tensile member to return to its free length, thus releasing the applied tensile force.
In the practice of applying tensile force by the application of a hydraulic fastener of the type hereinbefore described, should its internal seals fail, then the unit may become impossible to remove by usual means.
Previously used methods require that the locking ring which maintains the tensile load through the components of the hydraulic fastener be split into two or more pieces and removed from engagement to permit the bolt to regain its free length and relax the clamping force. It is possible to form a locking ring with a permanent bifurcation and securing method so that this operation can be performed more easily. It is, however, unavoidable that some damage will occur to the threads of engagement between the locking ring and its mating hydraulic fastener component. As hereinafter illustrated in the prior art example of FIGS. 1 and 2(a) to (c), as the semi-circular locking ring portion disengages from the hydraulic fastener body, then the force acting is progressively concentrated upon the remaining engaged portion of those threads, with consequential damage from overloading unavoidable.